Espalier, is a tree trained to a trellis instead of a wall, and though the fruit it bears is not quite equal to that borne by a tree of the same variety trained against the wall, yet it is far superior to that borne on either dwarf or full standards. Of this the causes obviously are, that the fruit and leaves are more fully supplied with sap, and more perfectly exposed to the light and warmth of the sun. Some gardeners object to their introduction into the kitchen garden on the plea that they deprive the under crops of air and light, but if confined to the borders of the main walks, the shelter they afford to those crops is more than commensurate to the slight interruption suggested. In addition, they are highly ornamental, and greatly improve the aspect of the kitchen garden. Espalier rails should run parallel with the walks, and at four feet distance from them; not higher than five feet; neat, and if made of wood, tarred, and the ends which are fixed in the ground charred; though blocks of stone sunk into the ground, with iron sockets or bases to receive those ends, are still better.

Gooseberries and Currants are highly improved by being trained as espaliers, and may be so grown along borders near the side walks of the kitchen garden. For these the trellis must be not higher than three feet from the ground, and for the purpose stakes about four inches in circumference, and thus arranged, are very suitable.

Fig. 41.

Various suggestions have been made for altering the form of espalier trellises, but let the gardener never adopt any that declines from the perpendicular.

The smallest approach to the horizontal increases the radiation of heat from the trees, and increases, consequently, the cold they have to endure at night. It is not one of the least advantages of training gooseberries and currants as espaliers, that it facilitates the protecting them with mats.